Experimental and theoretical investigation on shear performance degradation of GFRP bars in concrete after fire and high temperature
-
摘要:
玻璃纤维增强复合材料(GFRP)筋材凭借着其比强度高、耐腐蚀性能好、可设计性好等优点，被广泛应用于混凝土结构中，来解决因钢筋锈蚀而引起的混凝土结构耐久性退化问题。然而，与普通钢筋相比，GFRP筋力学性能呈现不同的高温劣化规律。目前对于GFRP筋拉伸性能研究较多，且多以裸筋为研究对象。本文考虑到工程中将GFRP筋替代普通钢筋的实际情况，且考虑到裸筋与结构内部筋材所处环境的差异，对高温后混凝土内GFRP筋水平剪切性能进行了研究。本文中，共选取100℃、150℃、200℃、300℃、350℃、400℃、500℃、650℃及800℃共9个温度工况，对GFRP筋混凝土试件进行高温作用，待筋材表面温度到达设定温度后恒温1h(部分工况恒温2h和3h)，冷却取出混凝土内筋材测试其水平剪切性能。试验结果显示：与裸筋相比，混凝土内的筋材表面存在明显温度滞后现象；混凝土未开裂时，其对内部筋材有良好的保护效果。内部筋材的水平剪切强度退化要慢于裸筋；混凝土的保护效果在开裂后基本完全消失，此时内部筋材的水平剪切强度退化规律类似于裸筋；即使混凝土未开裂，当温度超过筋材基体热分解温度时，随温度作用时间增加，内部筋材水平剪切强度近似呈线性下降趋势。结合试验与分析，本文给出了高温后混凝土内GFRP筋水平剪切强度预测模型。同时，以剪切强度保留系数0.7为设计基准，给出了不同保护层厚度下GFRP筋的耐火时间预测值，以期为GFRP筋工程结构的抗火设计及火灾后性能评估提供参考。 火灾中混凝土构件内部温度场Temperature field inside concrete components in fire GFRP筋水平剪切强度保留系数预测值Prediction of GFRP bar’s horizontal shear strength retention factors -
关键词:
- 火灾高温作用 /
- GFRP筋混凝土构件 /
- 水平剪切性能 /
- 预测模型
Abstract: To explore the shear performance of glass fiber reinforced polymer (GFRP) bars in concrete after fire and high temperature, nine temperature conditions of 100°C, 150°C, 200°C, 300°C, 350°C, 400°C, 500°C, 650°C and 800°C were selected to treat the GFRP bars placed in concrete, and the horizontal shear tests were carried out on the obtained bar specimens. The method of predicting the horizontal shear strength of GFRP bars in concrete after exposure to high temperature was discussed using the results of this study and some existing tests. Test and analytical results show that within 300°C there is a hysteresis phenomenon in the surface temperature of GFRP bars in concrete. Their high temperature deterioration is significantly lower than that of the bare bars, as well as the shear strength degradation is also relatively slow. As the temperature exceeds 300°C and the concrete surface cracks continue to develop, the deterioration of embedded GFRP bars caused by high temperature gradually enlarges, meanwhile, the shear strength decreases sharply, which shows a similar degradation pattern to that of bare bars. At high temperature of 300°C which is close to the thermal decomposition temperature of resins, the shear strength retention rate of GFRP bars decreases linearly from 76.4% to 46.5% with the constant temperature time increasing from 1h to 3h. Based on the hyperbolic tangent function model, a prediction model for the horizontal shear strength of GFRP bars in concrete after high temperature was established and model’s predictions were in good agreement with test values. Finally, considering a shear strength retention factor of 0.7, the predictions of fire resistance time of GFRP bars with different cover thickness were proposed, which can provide some references for engineering application. -
图 2 混凝土试件的热电偶布置及受热面
Figure 2. Thermocouple arrangement and heated surfaces of concrete specimens
图 5 不同温度工况下混凝土外观变化
Figure 5. Appearance changes of concrete under different temperature conditions
图 6 混凝土与筋材表面的升温过程对比
Figure 6. Comparison of heating processes between the surfaces of concrete and bar
图 7 高温后GFRP筋的外观形态
Figure 7. Appearance of GFRP bars after exposure to high temperatures
图 8 GFRP筋水平剪切的荷载-位移曲线
Figure 8. Load-displacement curves of GFRP bars in horizontal shear tests
图 9 GFRP筋的剪切破坏形态及端部详图
Figure 9. Shear failure modes and end details of tested GFRP bars
图 10 高温后混凝土内GFRP筋水平剪切强度保留率
Figure 10. Retention rate of horizontal shear strength of GFRP bars embedded in concrete after high temperature
图 11 高温后混凝土内GFRP筋水平剪切强度预测模型对比分析
Figure 11. Comparative analysis of prediction models for horizontal shear strength of GFRP bars embedded in concrete after high temperature
图 13 GFRP筋水平剪切强度保留系数预测值
Figure 13. Prediction values for horizontal shear strength retention factor of GFRP bars after high temperature
表 1 GFRP筋基本力学性能
Table 1. Basic mechanical properties of GFRP bars
Bar type Tensile strength /MPa Tensile elastic modulus /GPa Bending strength /MPa Horizontal shear strength /MPa GFRP 884.6 32.8 875.8 47.7 
下载: 导出CSV
表 2 混凝土配合比及基本参数
Table 2. Concrete mix ratio and basic parameters
Strength grade of concrete Water binder ratio Materials(kg·m−3) Measured compressive strength Water Cement Sand Stones C30 0.49 220 449 615 1116 33.8
下载: 导出CSV
表 3 不同温度工况下GFRP筋的水平剪切强度及保留率
Table 3. Horizontal shear strength and retention rate of GFRP bars under different temperature conditions
T/℃ F/N S/MPa Statistical characteristics R/% No.1 No.2 No.3 No.1 No.2 No.3 μ/MPa COV 20 7995.3 8607.5 7656.2 47.1 50.8 45.1 47.7 0.06 100.0 100 7791.4 7415.2 7379.4 45.9 43.7 43.5 44.4 0.03 93.1 150 6976.8 7375.1 7878.1 41.1 43.5 46.5 43.7 0.06 91.6 200 6480.6 6766.1 6707.3 38.2 39.9 39.6 39.2 0.02 82.3 300 6564.2 5134.5 6827.3 38.7 30.3 40.3 36.4 0.15 76.4 350 1654.7 1006.1 1335.2 9.8 5.9 7.9 7.9 0.24 16.5 400 315.5 1333.5 NA 1.9 7.9 NA 4.9 0.87 10.2 500 266.9 326.1 NA 1.6 1.9 NA 1.7 0.14 3.7 Notes：T is the temperature；F is the maximum load；and S is the horizontal shear strength；μ is the average value；COV is the coefficient of variation；R is the retention rate of horizontal shear strength；NA indicates that the corresponding value is not obtained。
下载: 导出CSV
表 4 300℃下不同恒温时间作用后GFRP筋水平剪切强度及保留率
Table 4. Horizontal shear strength and retention rate of GFRP bars after different constant temperature time at 300℃
t/h F/N S/MPa Statistical characteristics R/% No.1 No.2 No.3 No.1 No.2 No.3 μ/MPa COV 1 6563.3 5134.4 6828.3 38.7 30.3 40.3 36.4 0.15 76.4 2 5784.6 4268.1 5111.3 34.1 25.2 30.1 29.8 0.15 62.5 3 4315.8 3798.1 3232.1 25.5 22.4 19.1 22.3 0.14 46.5
下载: 导出CSV
表 5 不同保护层厚度下GFRP筋的耐火时间
Table 5. Fire resistance time for GFRP bars with different cover thickness
Case Case one Case two Case three C/mm 40 50 60 tf 65 83 190 Note: C is the thickness of concrete cover; tf is the fire resistance time.
下载: 导出CSV
-
[1] 叶列平, 冯鹏. FRP在工程结构中的应用与发展[J]. 土木工程学报, 2006(3):24-36. doi: 10.3321/j.issn:1000-131X.2006.03.004YE Lieping, FENG Peng. Applications and development of fiber-reinforced polymer in engineering structures[J]. China Civil Engineering Journal,2006(3):24-36(in Chinese). doi: 10.3321/j.issn:1000-131X.2006.03.004 [2] 陆春华, 吴小龙, 徐可, 等. 普通/钢纤维混凝土混合配筋梁裂缝和挠度计算分析[J]. 南京工业大学学报(自然科学版), 2022, 44(2):197-206.LU Chunhua, WU Xiaolong, XU Ke, et al. Calculation analysis of the cracking and deflection of ordinary/steel fiber concrete hybrid-reinforced beams[J]. Journal of Nanjing Tech University (Natural Science Edition),2022,44(2):197-206(in Chinese). [3] 王晓璐, 査晓雄. 高温下GFRP筋力学性能的试验研究[J]. 华南理工大学学报(自然科学版), 2011, 39(9):75-81.WANG Xiaolu, CHA Xiaoxiong. Experimental investigation into Mechanical Behavior of GFRP Rebars at Elevated Temperature[J]. Journal of South China University of Technology(Natural Science Edition),2011,39(9):75-81(in Chinese). [4] 李趁趁, 王英来, 赵军, 等. 高温后FRP筋纵向拉伸性能[J]. 建筑材料学报, 2014, 17(6):1076-1081. doi: 10.3969/j.issn.1007-9629.2014.06.024LI Chenchen, WANG Yinglai, ZHAO Jun, et al. Longitudinal Tensile Properties of FRP Bars after High Temperature[J]. Journal of Building Materials,2014,17(6):1076-1081(in Chinese). doi: 10.3969/j.issn.1007-9629.2014.06.024 [5] ASHRAFI H, BAZLI M, NAJAFABADI E P, et al. The effect of mechanical and thermal properties of FRP bars on their tensile performance under elevated temperatures[J]. Construction and Building Materials,2017,157:1001-1010. doi: 10.1016/j.conbuildmat.2017.09.160 [6] 朱德举, 徐旭锋, 郭帅成, 等. 高温后玄武岩和玻璃纤维增强复合材料筋的力学性能[J]. 湖南大学学报(自然科学版), 2021, 48(7):151-159. doi: 10.16339/j.cnki.hdxbzkb.2021.07.018ZHU Deju, XU Xufeng, GUO Shuaicheng, et al. Mechanical Properties of Basalt and Glass Fiber Reinforced Polymer Tendons after Exposed to Elevated Temperatures[J]. Journal of Hunan University (Natural Sciences),2021,48(7):151-159(in Chinese). doi: 10.16339/j.cnki.hdxbzkb.2021.07.018 [7] GUO Xiangke, XIONG chuansheng, JIN Zuquan, et al. A review on mechanical properties of FRP bars subjected to seawater sea sand concrete environmental effects[J]. Journal of Building Engineering,2022,58(15):105038. [8] SAWPAN M A. Shear properties and durability of GFRP reinforcement bar aged in seawater[J]. Polymer Testing,2019(75):312-320. [9] 屈凯. 真实火灾下钢筋混凝土板温度场有限元分析[J]. 硅酸盐通报, 2020, 39(6):1815-1821. doi: 10.16552/j.cnki.issn1001-1625.2020.06.018QU Kai. Finite Element Analysis on Temperature Distribution of Reinforced Concrete Slabs in Natural Fire[J]. Bulletin of the Chinese Ceramic Society,2020,39(6):1815-1821(in Chinese). doi: 10.16552/j.cnki.issn1001-1625.2020.06.018 [10] International Organization for Standardization. Fire resistance tests-Elements of building construction: ISO 834[S]. 1999. [11] 中国国家标准化管理委员会. 拉挤玻璃纤维增强塑料杆力学性能试验方法: GB/T 13096-2008[S]. 北京: 中国标准出版社, 2009.Standardization Administration of the People’s Republic of China. Test method for mechanical properties of pultruded glass fiber reinforced plastic rods: GB/T 13096-2008[S]. Beijing: China Standards Press, 2009(in Chinese). [12] American Society for Testing and Materials. Standard Test Method for Apparent Horizontal Shear Strength of Pultruded Reinforced Plastic Rods by the Short-Beam Method: ASTM Standard D4475-21[S]. West Conshohocken, PA, 2021. [13] 金浏, 张仁波, 杜修力, 等. 温度对混凝土结构力学性能影响的研究进展[J]. 土木工程学报, 2021, 54(3):1-18. doi: 10.15951/j.tmgcxb.2021.03.001JIN Liu, ZHANG Renbo, DU Xiuli, et al. Research progress on the influence of temperature on the mechanical performance of concrete structures[J]. China Civil Engineering Journal,2021,54(3):1-18(in Chinese). doi: 10.15951/j.tmgcxb.2021.03.001 [14] 蔡启明, 陆春华, 延永东, 等. BFRP和GFRP筋剪切性能的温度效应[J]. 建筑材料学报, 2022, 25(4):395-400. doi: 10.3969/j.issn.1007-9629.2022.04.010CAI Qiming, LU Chunhua, YAN Yongdong, et al. Temperature Effect on Shear Properties of BFRP and GFRP Bar[J]. Journal of Building Materials,2022,25(4):395-400(in Chinese). doi: 10.3969/j.issn.1007-9629.2022.04.010 [15] SAAFI M. Effect of fire on FRP reinforced concrete members[J]. Composite Structures,2002,58(1):11-20. doi: 10.1016/S0263-8223(02)00045-4 [16] NIGRO E, CEFARELLI G, BILOTTA A, et al. Guidelines for flexural resistance of FRP reinforced concrete slabs and beams in fire[J]. Composite Part B:Engineering,2014,58:103-112. doi: 10.1016/j.compositesb.2013.10.007 [17] ZHOU C H, Pan J J, Zhang Z H, et al. Comparative study on the tensile mechanical behavior of GFRP bars under and after high temperature exposure [J]. Case Studies in Construction Materials, 2022, e00905. [18] MOURITZ A P, GIBSON A G. Fire properties of polymer composite materials[M]. Dordrecht: Springer, 2006. [19] BISBY L A. Fire behaviour of fibre-reinforced polymer (FRP) reinforced or confined concrete[D]. Queen's University at Kingston (Canada), 2003. [20] 住房与城乡建设部, 国家质量监督检验检疫总局. 建筑设计防火规范: GB 50016-2014(2018)[S]. 北京: 中国计划出版社, 2018.Ministry of Housing and Urban Rural Development, General Administration of Quality Supervision, Inspection and Quarantine. Code for Fire Protection Design of Buildings: GB 50016-2014(2018)[S]. Beijing: China Planning Press, 2018(in Chinese). [21] 建设部, 国家质量监督检验检疫总局. 混凝土结构设计规范: GB 50010-2010(2015)[S]. 北京: 中国建筑工业出版社, 2015.Ministry of Housing and Urban Rural Development, General Administration of Quality Supervision, Inspection and Quarantine. Code for design of concrete structures: GB 50010-2010(2015)[S]. Beijing: China Architecture Press, 2015(in Chinese). [22] HAJILOO H, GERRN M F, Noël M, et al. Fire tests on full-scale FRP reinforced concrete slabs[J]. Composite Structures,2017,179:705-719. doi: 10.1016/j.compstruct.2017.07.060 [23] 肖明辉, 时旭东, 邢万里. 不同等级混凝土强度高温衰退性能试验研究[J]. 建筑结构, 2009, 39(7):113-115. doi: 10.19701/j.jzjg.2009.07.034XIAO Minghui, SHI Xudong, XING Wanli. Experimental research on strength decaying of concrete with different grades at elevated temperature[J]. Building Structure,2009,39(7):113-115(in Chinese). doi: 10.19701/j.jzjg.2009.07.034 [24] American Concrete Institute (ACI). Guide for the Design and Construction of Structural Concrete Reinforced with FRP Bars: ACI 440.1 R-15[S]. Farmington Hills, MI, USA, 2015. [25] 住房与城乡建设部, 国家市场管理监督总局. 混凝土结构耐久性设计标准: GB/T 50476-2019[S]. 北京: 中国建筑工业出版社, 2019.Ministry of Housing, State Administration for Market Regulation. Standard for design of concrete structure durability: GB/T 50476-2019[ S]. Beijing: China Architecture & Building Press, 2019 (in Chinese). -
下载:
点击查看大图
计量
- 文章访问数: 105
- HTML全文浏览量: 62
- 被引次数: 0
